Alternating Current (AC) devices, such as an air conditioner, a refrigerator and a washing machine, are driven by a commercial electric power (AC power), and Direct Current (DC) devices, such as a personal computer, a Liquid Crystal Display (LCD) television, a telephone and a facsimile, are driven by a DC power. In this regard, there is proposed a technology that operates in parallel an AC power distribution system for supplying an AC power and a DC power distribution system for supplying a DC power in a house or a shop (see, for example, Japanese Patent Application Publication No. 2009-178025).
In household power distribution systems, a commercial power source, solar cells and a secondary battery charged with a surplus power are commonly used as power supply sources which supply powers to devices. Furthermore, the power supply source(s) that supplies the power to the devices is switched based on an amount of power supplied and an amount of power required.
For example, while the power charged in the secondary battery or the power generated by the solar cells is sufficient, the power charged in the secondary battery or the power generated by the solar cells is not only supplied to the DC devices, but is also converted into an AC power using an inverter and supplied to the AC devices. Furthermore, when the power charged in the secondary battery or the power generated by the solar cells is insufficient, the power supplied by the commercial power source is not only additionally used and supplied to the AC devices, but is also converted into a DC power using a converter and supplied to the DC devices.
However, although the power supply source(s) which supplies the power to the devices is switched depending on the amount of the power supplied by the power supply source(s) and the amount of the power required by the devices, the operations of the devices are kept constant regardless of the switching of the power supply sources. Therefore, it is unable to perform an efficient power saving control in which the operations of the power supply sources are carried out in association with the operations of the devices.